add a command to sector map, orders, whichever, to allow ordering NPC piloted ships to transfer cargo from one to another, possibly as a 'standing' order... IE you have a cargo vessel specifically used for trading/hauling general goods.. that ship can be ordered to fly to other ships in sector and 'request' their trade goods. or a ship regularly sent on refining 'missions' can be ordered to periodically check for and retrieve scraps or ore from other ships in sector, keeping their cargo bays clear for collecting more of the resources.